Assistant Secretary - Indian Affairs Tara Sweeney announced today that the Department of the Interior has signed agreements with the Oglala Sioux Tribe of the Pine Ridge Indian Reservation in South Dakota, the Northern Cheyenne Tribe of the Northern Cheyenne Indian Reservation in Montana, and the Santee Sioux Nation of the Santee Sioux Reservation in Nebraska to guide implementation of the Land Buy-Back Program for Tribal Nations at each of these reservations.